1. Field of the Invention
This invention relates to a three-layer, double biased structural fabric, more particularly to a three-layer double biased structural fabric which is especially designed to be lightweight and yet exhibit high stiffness and torsion resistance qualities.
2. Description of the Prior Art
Structural fabrics which are made on a bias, i.e., where the material of the fabric is aligned at an angle to the longitudinal center line of the fabric, have hitherto been known. It has also been known to provide a multilayer fabric, with different layers biased in different directions, to provide a structural fabric with strength in more than one direction, specifically, in the directions of the different angles of alignment. However, where such structural fabrics have been employed, due to the fact that they are far lighter than the structural materials they are used to replace, such as steel, a number of defects have appeared. One of these defects is that the structural fabrics of the prior art lack the stiffness of the corresponding structural materials such as steel and wood. Another defect is that these structural fabrics, even when biased, exhibit low or insufficient torsional resistance for certain applications. Thus, where the application of such fabrics involves their use in a device which is subjected to high torsional stresses, the lack of torsion resistance can only be overcome, if at all, by the addition of many layers of fabric, which defeats the twin goals of a lightweight structural material that is relatively inexpensive and easy to prepare.